1. Field of the Invention
The present invention relates to a wet electrophotographic printer and, more particularly, to a wet electrophotographic printer capable of preventing peripheral devices such as a photoreceptor belt from being contaminated by ink which flows outwardly at both ends of a plurality of rollers after being used for a development process.
2. Description of the Related Art
In general, a wet electrophotographic printer emits a laser beam onto a photoreceptor such as a photoreceptor belt to generate an electrostatic latent image, develops the electrostatic latent image by using a developer liquid which is normally mixed with a toner in a solid state having a predetermined color, and a carrier in a liquid state functioning as a solvent, and produces a desired image on a paper through transcription.
In FIG. 1, there are shown major components of a wet electrophotographic printer as described above. A photoreceptor belt 1 is trained over rollers 2, 3, and 4 mounted within a main body of the printer (not shown), to run or circulate therearound. An electostatic latent image is formed on the photoreceptor belt 1 by a beam exposing device (not shown), and then is developed by a developing device 10. An image formed on the photoreceptor belt 1 by the developing device 10 is dried by a drier 20, up to a level required for transcription, and finally is transcribed in a transcriber 30 onto a paper supplied from the outside.
The developing device 10 is provided with a plurality of development units (normally four), each of which corresponds to a color. Representative of other development units, development unit 11 includes a development roller 13 for transcribing a developer injected from a developer injection nozzle 12 onto a region of the electrostatic latent image on the photoreceptor belt 1, and a squeegee roller 14 for removing the carrier from the developer transcribed onto the photoreceptor belt 1. Although not shown in the drawings, a cleaning roller for removing sludge of the developer smeared around the squeegee roller 14 is provided in the developing device 10.
When the electrostatic latent image of the photoreceptor belt 1 arrives at the development roller 13, the toner contained in the developer is moved to the region of the electrostatic latent image on the photoreceptor belt 1 to adhere thereto, due to an electric potential difference between the region of the electrostatic latent image and the development roller 13. Since a portion of the photoreceptor belt 1 unexposed to the beam has a higher electric potential than that of the development roller, the developer is smeared on the belt 1 rather than the toner. The electrostatic latent image is filmed over with a portion of the toner adhering to the electrostatic latent image by the squeegee roller 14 depressing the photoreceptor belt 1, and the developer with the rest of the toner is removed by the squeegee roller 14.
The development is performed in such a manner so that the development roller 13 and the squeegee roller 14, both in close contact to the photoreceptor belt 1, depress the photoreceptor belt 1, thereby spreading the developer over the rollers 13, 14. Consequently, the remaining developer not used for the development process is driven or pushed out toward both ends of the rollers 13, 14. The rollers 13, 14 may be contaminated with the remaining ink, i.e., the ink pushed out which pollutes the peripheral devices including the photoreceptor belt 1.
In FIGS. 2 through 5, a conventional ink contamination prevention device for preventing the contamination by the remaining ink described above is shown. The conventional ink contamination prevention device is provided with a pair of protrusions 40, 40xe2x80x2 for stopping a flow of the ink toward both ends of the development roller 13.
As shown in FIG. 4, the ink contamination prevention device constructed in this manner can prevent the remaining ink 100 from flowing to the outside of the development roller 13, since the protrusions 40, 40xe2x80x2 stop the flow of the remaining ink 100.
However, as shown in FIG. 5, since the protrusions for stopping the flow of the remaining ink are formed in a simple annular shape around a shaft of the development roller 13 in the conventional ink contamination prevention device, when the development roller 13 rotates, there is a possibility of the remaining ink 100 accommodated in recesses defined by the protrusions 40, 40xe2x80x2, flowing to the outside of the development roller 13 beyond the protrusions 40, 40xe2x80x2. That is, stopping the flow of the remaining ink 100 is not fully achieved, thereby polluting the roller and the peripheral devices and degrading the lifetime of those components. Further, if the contamination by the remaining ink described above occurs in the squeegee roller 14, the remaining ink may flow from an end of the squeegee roller 14 to the photoreceptor belt 1 to pollute the same, causing a degradation of the quality of the print.
It is, therefore, a primary object of the invention to provide an ink pollution prevention device capable of preventing remaining ink from polluting rollers, peripheral devices, and a photoreceptor such as a photoreceptor belt by fully stopping a flow of the remaining ink toward the outside of a roller at both ends of the roller.
In order to achieve the object, the present invention provides an ink pollution prevention device in a wet electrophotographic printer, for preventing a developer from polluting a photoreceptor and peripheral devices by flowing out at the ends of a development roller, a squeegee roller, and a cleaning roller to the outside of the rollers. The device is provided with a pair of ink stoppers, with stoppers disposed around both sides of a shaft of each roller in a symmetrical manner with each other. Each ink stopper has a plurality of peaks and recesses which form a continuous helical shape in an opposite helical direction from the other ink stopper. The helical shape of the ink stopper is oriented so as to permit the ink in the ink stopper to flow toward the center of the roller along the recesses, when the roller is rotated.
The ink stopper can be integrally formed with a shaft of each roller or independently formed and mounted on the shaft, as a fixed member.